Engine manifold pressure simulating apparatus for aircraft ground trainers



March 7, 1950 J. J. LuKAcs ENGINE MANIFOLD PRESSURE SIMULATING APPARATUS FOR AIRCRAFT GROUND TRAINERS 2 Sheets-Sheet l Filed July 31, 19.46

March 7, 1950 J. J. LUKAcs 239499597 ENGINE MANIFOLD PRESSURE SIMULATING APPARATUS FOR AIRCRAFT GROUND TRAINERS l Filed July 51, 1946 2 Sheets-Sheet 2 MOTOR UN/ T a ALT/METER RPM. ,4/6

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PRESSURE RPM Moron u/v/T /2 AN /NI//VTOR N JJ. LUKACS 5V TTORNEV Patented Mar. 7, 17.950

ENGINE MANIFOLD PRESSURE SIMULATIN G APPARATUS FOR AIRCRAFT GROUND TRAINERS Joseph J. Lukacs, New Rochelle, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 31, 1946, Serial No. 687,471

14 claims. 1

This invention relates to an aviation trainer and more particularly to circuits and apparatus which simulate the functioning of the manifold pressure regulator used in conjunction with water injection whereby when the cockpit throttle control is set by the pilot for a desired manifold pressure, such pressure is automatically maintained up to the critical altitude. The circuits also simulate the ram effect on the manifold pressure due to high air speeds.

In airplanes of certain types a manifold pressure regulator is provided for automatically maintaining a desired manifold pressure. The regulator is provided on one side of its casing with a lever which is connected by a suitable linkage with the pilots throttle control quadrant, and with a lever on the opposite side of the casing which is connected by suitable linkage with the carburetor throttle lever. The pilots throttle control quadrant is movable through an angle of 90 degrees whereas by mechanical linkage the throttle lever is movable through an arc of approximately 29 degrees. Three pipes enter the regulator the first of which connects the intake manifold of the engine with a Sylphon bellows in the regulator whereby the Sylphon bellows takes an adjustment which varies with the manifold pressure, The second pipe is connected with the supercharger blower speed control valve so that the change in oil pressure in such pipe when the valve is operated to shift the blower gears to drive the blower at a high or at a low speed, the regulator is reset in accordance with such shift. The third pipe is connected to the antidetonant water injection regulator whereby the manifold pressure regulator is reset by water pressure applied through the pipe when anti-detcnant injection operation of the engine is being had. The manifold pressure regulator is also provided with a hydraulically operated servo system which is responsive to the manifold, oil and water pressures applied through the three pipes to effect a variable coupling between the two levers before mentioned.

The operation of the manifold pressure regulator is accomplished by the actuation of the pilots control lever of the regulator in response to the operation of the throttle quadrant until the desired manifold pressure is obtained. The regulator will then maintain this manifold pressure within the limits of its design and the limits of engine performance regardless of engine R. P. M., altitude or air speed.

The pilots control lever is interconnected within the regulator to the carburetor throttle actuating lever in such a manner that the -carburetor throttle is mechanically operated by movement of the pilots control lever for the rst 22 degrees of throttle quadrant movement. This, accordingly, opens the carburetor throttle approximately 8 degrees, In general, this throttle opening or minimum throttle angle provides for manual control of the engine for starting, idling and taxiing.

As the rotation of the pilots throttle control lever is increased the selected manifold pressure will be somewhat higher than that which would normally be obtained by manual operation of the carburetor throttle and consequently the hydraulic servo system within the regulator must open the throttle further to automatically obtain and regulate the selected manifold pressure. Therefore, while full travel of the pilots control lever will mechanically provide a maximum of 29 degrees of throttle lever travel, the hydraulic servo system will automatically open the throttle so that the selected manifold pressure is secured.

It should be noted that at 53.5 degrees rotation of the pilots control lever Normal rated power manifold pressures are obtained in both high and low blower ratios and at degrees rotation Military power manifold pressures in both high and low blower ratios are realized. Separate schedules of manifold pressure selection versus pilot control lever position are used for low blower ratio, high blower ratio and anti-detonant injection operation. When the mode of engine operation is changed by the pilots use of any of these types of operation, the manifold pressure regulator automatically shifts from one manifold pressure regulator schedule to another. However, the manifold pressure regulator does not actuate the shift from low to high blower ratio or the reverse nor does it cause the anti-detonant injection system to function. Normal controls are still required to operate the supercharger speed selector Valve and the anti-detonant injection equipment.

When making a Military or Normal rated power climb the pilot can shift from low blower to high blower ratio and the manifold pressure regulator will automatically maintain the manifold pressure at the required value without requiring a change in the position of the throttle control. The change of the manifold pressure schedule following the supercharger blower clutch shift is accomplished within the regulator itself by the introduction of high ratio clutch oil pressure through the second pipe above referred to. Con' versely, when the blower ratio is shifted from high to low, the loss of high ratio clutch oil pres- 3 sure resets the manifold pressure to the low blower ratio schedule.

The anti-detonant injection manifold pressure schedule is accomplished in a similar manner by pressure applied to the third pipe above referred to when the anti-detonant injection system is operated. The maximum manifold pressure which can be obtained under the anti-detonant injection operating condition is adjustable to suit the varying speeds as dictated by individual types of installation. If the anti-detonant system is turned on in the manifold pressurev range where the anti-detonant injection manifold pressure is higher than the operational (low or high blower ratio) manifold pressure, the regulator will immediately open the carburetor throttle to provide the selected anti-detonant system manifold pressure provided that this can be obtained within the range of full throttle operation. When the anti-detonant system is turned off or if the antidetonant liquid supply is exhausted, the antidetonant pressure of course immediately fails and the manifold pressure is reset by the regulator to the low or high blower ratio dictated by the pilots throttle lever position.

Should the oil supply to the manifold pressure regulator fail, the piston of the servo-system is immediately forced to its full decreased position by the action of a spring and manual control of the carburetor throttle is then obtained. The relative motion of the pilots control lever to that of the carburetor throttle lever is thereby rendered identical to that which is obtained when the engine is shut down. In other words, full 90 degrees travel of the pilots control lever will result in approximately 29 degrees travel of the carburetor throttle lever. This is suflicient to give a throttle opening at sea level corresponding to 47 inches of mercury of manifold pressure in high blower and 41 inches of mercury of manifold pressure in low blower at 2800 revolutions per minute.

The manifold pressure sensitive bellows of the regulator consist of the manifold pressure vented bellows connected as previously stated through rthe rst pipe to the engine intake manifold balanced against an evacuated bellows. In the event of failure of the evacuated bellows, the manifold pressure selection schedules are increased by the amount of absolute drain oil pressure existing in the regulator. However, in order to permit operation at low power, a feature known as low boost lock-out operates through the first nine degrees ofv the pilots throttle control lever travel. The power obtained in this range is identical to the manual schedule available for idling and taxiing as described for normal operation.

In an airplane it is customary to position the intake air scoop for the carburetor sol that the maximum amount of air is supplied and therefore the scoop is directed forwardly. The result is that as the air speed increases, a ram effect is produced which increases the pressure of the air directed to the carburetor and thus increases the effective manifold pressure of the engine. This ram effect is proportional to the indicated air speed. For example, as the air speed increases to 200 knots the ram effectl will produce an increase in the manifold pressure of about two inches of mercury and if the air speed increases to 400 knots the ram effect will produce an increase in the manifold pressure of about six inches of mercury. It is thus apparent that the ram effect is very advantageous in increasing the d power of the airplane and thus increasing the ceiling of its flight.

It is an object of the invention to enable the simulation of the operation of a manifold pressure regulator to regulate the manifold pressure of an airplane engine in accordance with the setting of the engine throttle for a desired value of manifold pressure.

A further object of the invention is to enable the simulation of the increase in manifold pressure due to the ram effect.

The rst of these objects is attained by the provision of a rst or manifold pressure re-gulator motor unit the shaft of which may be moved to positions representative of the desired manifold pressures for the several angles of throttle opening in accordance with the operating schedules for the particular airplane engine which is being simulated whereby a second or manifold pressure motor unit is controlled to cause a manifold pressure indicator to indicate the required manifold pressure. The manifold pressure regulator motor unit is responsive to throttle control, to anti-detonant or water injection control, and to supercharger blower speed control in simulation of the response of the regulator of an actual airplane to such controls.

The second of the stated objects is attained by the provision of a potentiometer the slider of which is advanced as the indicated air speed increases to apply an increasing value of signal potential to the manifold pressure motor unit of a phase which will cause such unit to operate in a manner representative of an increase in manifold pressure as the indicated air speed increases.

Other features of the invention will become apparent upon the consideration of the following detailed description of the invention when read in connection with the accompanying drawings in which:

Fig. 1 shows in the upper left portion thereof instruments, controls and lamp signals at an instructors desk; in the lower left portion thereof controls in the cockpit of the trainer and in the right portion thereof relays controllable by the controls at the instructors desk and in the cockpit for controlling the apparatus of Fig. 2; and

Fig. 2 shows portions of the manifold pressure motor unit for simulating the development of manifold pressure in the intake manifold of an airplane engine, the schematic representation of the manifold pressure regulator, R. P. M., altimeter and indicated air speed motor units of the trainer, and portions of the engine control circuit.

For a complete disclosure of the invention Fig. 2 should be placed to the right of Fig. 1.

The motor units disclosed in Fig. 2 are each of the type disclosed in the application of Albert- Davis-Gumley-Holden, Serial No. 562,434, led September 15, 1943, which issued as Patent No. 2,428,767 on October 14, 1947. To simplify the drawings, the control circuit ofonly one of vthese motor units, the manifold pressure motor unit, has been disclosed in detail, the other motor units being shown skeletonized to merely show such potentiometers thereof as are deemed necessary for an understanding of the invention.

The manifold pressure motor unit comprises a rst dual vacuum tube VT! which serves as a two-stage resistance coupled amplifier to amplify the control signal applied over contr-ol conductor 200 through the gain control rheostat Rl and to apply the amplied signal potential to the primary winding of the step-up input transformer TRI. The amplified signal is impressed from the lower secondary winding of the transformer through the dual diode tube VT3, serving as a full wave rectifier, upon the control grid of the motor impulsing thyratron tube MI and the signal is also impressed from the upper secondary Winding of transformer TRI upon the control grid of the left unit of the dual tube VT2 which further amplifes the signal and impresses it upon the control grid of the motor reversing tube MR. Grid bias is supplied to the control grid of the thyratron tube MI from the right secondary Winding of the filament supply transformer TR2, through the right unit of tube VT2, serving as a rectifier, and such bias is adjusted by the grid bias adjusting rheostat R2. Cathode bias is applied to the cathode of the tube MR from the potential divider comprising the bias adjusting rheostat R3, the resistor 20| and battery.

Tube MI upon firing causes the transmission of positive impulses of current through the rotor circuit of the motor M from the 115volt phase p2 source of alternating current Tube MR upon ring causes the operation of the anode relay RV which in turn causes the operation of the stator circuit reversing relay RVI. The stator winding of the motor M is energized in a circuit over the contacts of relay RVI from the source of -l-lBO-volt direct current.

Cathode heater current is supplied to the filaments of tubes VTI, VTZ, VT3 and MR, from the left secondary winding of the filament supply transformer TR2 and heater current is supplied to the filament of tube MI from the middle secondary Winding of transformer TR2. Anode potential is applied to the anodes of tube VTI from the source of -l-lSll-volt direct current. Anode potential is supplied from the source of 115-vo1t phase p2 potential through choke coil 202 to the anode of tube MI and through the ballast lamp 203 and through the winding of relay RV to the anode of tube MR.

The tube MI is normally negatively biased to a point just below the critical breakdown potential of the tube over a biasing circuit which extends from the grid of the tube through resistors 253 and 254 through the bias control rheostat R2, through the right rectfying unit of tube VT2 and the right secondary winding of filament supply transformer TR2 to ground. When sigmaling potential is applied to control conductor 200, is amplified by tube VTI and the amplied potential is impressed upon the lower secondary winding of input transformer TRI, such amplied potential is rectied by the tube VT3 and applied to the grid of tube MI and the negative biasing potential on the grid is thus made less negative so that the tube lires on each positive half cycle of the anode potential applied to its anode. Each time that tube MI fires, an impulse is transmitted through the armature circuit of motor M over a path which may be traced from the 115- volt p2 source of anode potential through choke coil 202, over the anode-cathode path through tube MI, over the mid-tap connection of the middle secondary winding of transformer TR2, through the armature circuit of the motor M, the back contact of the LS relay and to ground.

The motor M, through the reduction gearbox 204, drives the shaft 205 in one or the other direction at a slow speed dependent upon the operated or unoperated condition of relay RVI and, through pairs of gears such as 206 and 201, drives the sliders of potentiometers such as MPI and through gears 208 and 209 drives the rotor of the synchro-transmitter ST. Only that one of the potentiometers driven from the shaft 205 which enters into the control of circuits relating to the present invention has been disclosed. The shaft 205 also has secured thereto cams 2|0 and 2I| which control the LI and L2 limit switches to cause the rotation of the motor M to cease when the sliders of the potentiometers approach the Nos. 1 or 3 terminals of the potentiometer windings, respectively.

The rotor winding of the synchro-transmitter ST is energized from the 28-volt, 40G-cycle source of alternating current and the stator windings of synchro-transmitter ST together with the supply conductors from the 40G-cycle source are connected over conductors of cable 2 I 2 with the corresponding winding terminals of the stator and rotor windings of the synchro-receiver SR at the instructors desk. The rotor of the synchro-receiver is coupled to the manifold pressure indicator |00, the needle of which is thereby rotated to a position corresponding to the movements of the rotor of synchro-transmitter ST and of shaft 205.

The engine control circuit for simulating the control of the operation of an engine of an airplane has been schematically disclosed in the lower right portion of Fig. 2. This control circuit is of the general character fully disclosed in the application of J. J. Lukacs and W. B. Strickler, Serial No. 542,846, fiiled June 30, 1944, in the application of F. M. Burelbach and J. J. Lukacs, Serial No. 679,069, led June 25, 1946, and in the application of C. E. Germanton, Serial No. 622,- 070, filed October l2, 1945. Only a few of the relays of the control circuit have been disclosed, the ESTI and EST2 relays 2|3 and 2|4 which are both energized when the starting of the engine has been simulated, the AS and ASI relays 2I5 and 2 I 5 which are both operated as soon as simulated air speed has been attained, the PUL and PULI relays 2| 'I and 2I8 which are both operated When the feathered condition of the blades of the engine-driven propeller has been simulated, and the ALT relay 2 I9 which becomes operatedwhen the pilot has set the carburetor air control into the alternate air position. y

At the instructors desk of Fig. l, a manifold pressure control potentiometer MPP whereby the instructor may introduce a desired manifold pressure control for training purposes, a key |0| for controlling the application of the anti-detonant or water injection operation, a key |02 for simulating the disabling of the Sylphon bellows of the manifold pressure regulator, a key |03 for simulating the disabling of the servo system of the regulator, circuit breaker throw-out switches |04, and lamps |06 to |09, inclusive, for indicating the operated positions of controls in the cockpit of the trainer operable by the pilot are provided.

In the cockpit of the trainer, Fig. l, the throttle lever |I0 is provided. This lever is secured to a shaft III to which the cams ||2 and ||3 and the gear I I4 are secured. The cams are effective to operate the contact sets I I5 and IIB associated therewith, the contact set ||5 being held in the position shown until the throttle lever ||0 has been moved through 9 degrees of its operating movement, and the ycontact set I IIB being held in the position shown until the throttle lever has been moved through 22 degrees of its operating movement. The gear I I4 through the pinion I Il drives the shaft |52 to which the sliders of the 'aerea-nef? 7 :throttle potentiometersTl ,T12 vand T3 faresecured. flhelcam ||`8 'is operable from the shaft ||.|.,=and

operates theassociated contact .set .H9 to its :alternate position during the iinal 15-degree movement of the throttle lever, or between the ledegree and Sil-degree throttle positions. Y'If =a two-engined airplane is being simulated, a cam vsimilar to `cam :inl-Swould be operated'from a similar throttle `operated shaft to control a `Contact set similar to H9 connected in parallel with contact set ||9 or the cam H8 could be arranged -to be operated from 'either throttle operated shaft. vA supercharger control lever 2|? is also provided, .which when operated rotates thecam |2| to close the low .blower `speed switch when rotated 90 degrees from normal, and 'to close the high blower speed switch when rotated 180 degrees :from normal. A water injection control switch :i12-2 Vof the circuit breaker type and ia battery powerfon switch |23 are also yprovided inthe cockpit.

:Until thestarting of the engine is simulated, the 'ESTL ESTZ, AS and ASi relays .2|3,12-|,.21|5 and *211;6 .remain unoperated. With no air speed yet developed, the slider of the indi-cated air speed potentiometer IAST will be at the No. l -terminal of itswinding andthe slider of the altimeter potentiometer AI'B will be at the No. 1 terminal Aof its winding. The winding or" `potentiometer IAS? is energized in a lcircuit extending from ground through the right Y,half yof l:the secondary ywinding of ytransformer TRS,y over `Vthe .lllrpl lbus bar, through the potentiometer winding and `through resistor '22D to ground. The rst half o'f the potentiometerwinding is shunted by resistor 22| softh-atwhen air speed 'is attained, the potential derived "at the slider otsuch potentiometer will increase vat one rate until an airspeed 'of about 215 knots is reached :and will increase at .a'faster rate until the upper speed430 knots is reached.

The Vpotential lderived from `the vslider of :potentiometerIASi is :applied throughthe winding ofthe altimeter'potentiometer M6 and through resistor .222 to ground whereby potential 'of phase p1 :is-derived at the slider ofthe latter potentiometer andapplied .over the lower back contact of the EST2 .relay 2M, over the ,lower back contact of the AS1 relay Mt and to ground through the potential .divider comprising resistors 223 and 224. The potential thusproduced at the junction point between resistorsZt and 221i is then appliedgover the lower back ycontact of the AS relay 2lf5, Aover the upper yinner back contact of the EST! relay 2|;3 vand through the summing resistor 225to'the signa-l'input'conductor:2ER or" the manifoldipressurevmotor'unit.

lAt -this time, lsince the engine is `not running, the shaft of the R. P. M. motor unit Vwill'not-have been'moved from its normal position, representa'- tive of no engine speed, and therefore the slider vof .the-R. P. 4potentiometer RPMS will beat the No. 1 or grounded terminal of its winding and ground potentialwill therefore be `applied from such .slider through the summing resistor 228 to signal input conductor `iti! of the manifold pressure motor unit. This ground potential -will lalso Vbe applied through summing resistor 25| tothe-'signal input conductor 25B of the manifold pressure regulator motor unit. 4Ground potential willalso be applied :from the-upper back contact of the -ESTZ relay 'l2-Ill Yoi .the `enginefcontrol.circuit, .through .summing resistor V22.@ to signal input-con-ductor 2.59, since-itis-assumed that the starting of the yengine has net yet beensimulated.

'The "potential of phase p1 :applied to conductor 200 Ias previously A'described is :amplified by tube VTiI and the ampliedsignal kpotential then -ef- -fective to cause 'the motoreimpulsing tube lVlI to lire and transmit impulses of current-through the rotor Acircuit of motor M, `but the :phase of the `portioniof the signal potential which becomes impressed Athrough tube V'YIZ upon Athe control grid of the motor-reversing tube MR wil-l -be opposite to l.the phaseo'f the anode potential applied `from the source of volt phase p2 potential land Aconsequently Stube kMIE?. will not re Aand relays RV and RV-I will remain unoperated. With relay RVI unoperated, the stator winding of the motor M'will be energized in such a manner .that upon the -energization of 'theroftor `circuit by the ring of itu'be lVH, the motor M, through the reduction gear box 204, will turn the shaft 255m a direction representative -of :an increase `in manifold pressure.

As the shaft 205 rotates, the slider of the balancing potentiometer MPI is rotated towards the No. 3 terminal ofthe potentiometer winding. The winding yof this ypotentiometer is energized over `a circuit extending from the junction point between the resistors -o'f vthe potential divider eX- tending Vfrom ithe 40qi2 ibus lbar through resistors 239 and 273.1! to ground, thence through the windingof potentiometer and through resistor 232 to ground. An increasing value of phase c2 potential is thus derived'fromrthe-sliderof this potentiometer .as `it moves towards the N o f3 terminal of the winding :and this potential .is applied through summing resistor .23.3 .to signal input Vconductor 28d. When 'the 'value o'f :the phase p2 potential thus applied to conductor '20B balances lthe phase p1 signal potential, the tube VTi will .cease to transmit :a signal `potential to the control grid of tube .MI and .such tube will cease transmitting driving *impulses 'through the `rotor ycircuit of motor 3M and 'the motor will come to rest `with the shaft i205 rotated into a position representative of the barometric pressure at sea '.level.

This Yposition .of shaft 265 is communicated to thefrotor of `synchro-transmitter ST which in the well-:known :manner will Acause the rotor of the synchro-receiver SR to vassume a corresponding position to move thefneedlefof the manifold vpressure indicator |90 at the instructors desk into a position to indicate `the sea level .barometric pressure of A30 inches ofmercury.

With'thethrottleiclosed at'this time and therefore the slider of throttle potentiometerTZ at vthe No. 1 terminal of its winding, ground potential willf'be applied from the `lowerbaclr contact of the SYFirelay |28, .overthe loweriback contact ofthe SHR rela-y |29 to the INo.` 1 .terminal of Athe throttle potentiometer T2, thence over the slider of such potentiometer, over the back contact of the WI relay |30, over conductor I3! and through thesumm'ing resistor 252 tothe signal input conductor'25 of the manifold pressure regulator rnc-- tor unit. As previously described ground potential is at .this time applied to conductor through Asumming resistor 25|. However, signal potential .of .phase pl .is at this time applied to conductor 25|) 4from the 40p1.bus.bar, through resistor 23d, over :the upper `back contact of the AS relay A2|5, over the upper 4back .contact of the ESTI ,relay .2 3.and'through summing resistor 253 to ,conductorv25- Thusinresponse to'this phase pil potentiaLthe manifold pressure regulator motor unit'rotates its shaft to the full extent of its movement or untilstpped by the operationof the;

L2 limit switch of such unit. This motor unit, is, however, without function at this time.

It will now be assumed that the starting of the engine is simulated by the pilot and as a result the EST! and ES'I'2 relays 213 and 214 both operate and the sliders of the RPM8 and RPMS potentiometers move away from the No. 1 terminals of the potentiometer windings to positions representative of the idling of the engine at an assumed speed of about 500 R. P. M. The phase p1 potential previously applied to signal input conductor 200 of the manifold pressure motor unit from the junction point between resistors 223 and 224 of the potential divider circuit previously traced from the slider of the altimeter potentiometer A16, over the lower back -contact of the ESTE relay 214 and the lower back contact of the AS1 relay 215 through resistors 223 and 224 to ground, is now applied from the slider of potentiometer A16 over the lower front contact of relay 214, over the back contact of the ALT relay 219, it being assumed that the pilot has selected the direct air supply for the carburetor and relay 219 is not therefore operated, and thence by two parallel paths to ground. One of these paths extends over the middle upper back contact of the SHR relay 235 through resistor 243 to ground and the other of the paths extends through resistor 236, over the upper back contact of relay 235, through the winding of the R. P. M. potentiometer RPMS, over the lower back contact of relay 235 and through resistors 23'1 and 238 to ground. At this time the lower half of the winding of potentiometer RPMS is shunted over the inner upper back contact of relay 235 and through resistor 239 whereby as the slider of the potentiometer moves from the No. 1 terminal to the mid-tap terminal of its winding, the potential derived at the slider will increase at one rate until an engine speed of approximately 1600 R. P. M. is attained and will then increase at a faster rate until the upper limit of the engine speed of 3200 R. P. M. is attained.

The phase p1 potential derived at the slider of potentiometer RPMS is then applied over the inner front contact of the ESTI relay 213 and through the summing resistor 225 to signal input conductor 200 of the manifold pressure motor unit. This potential will be less than the potential of phase p1 previously applied to conductor 2130 so that now the phase o2 potential applied to conductor 201] from the slider of the manifold pressure balancing potentiometer MP1 through summing resistor 233 will overbalance the phase fpl potential and consequently the phase o2 potential applied to the control grid of tube MR will cause such tube to ilre and to cause the operation of the RV and RVI relays. At this time the phase e2 potential will, due to the full wave rectiiication aiforded by tube VT3, cause tube Ml' to respond and to transmit power impulses of current through the rotor circuit of motor M. With relay RVI now operated, current from the +130 volt source of direct current is now applied to the stator circuit of the motor M in such la direction that in response to the power impulses motor M now turns the shaft 205 in a direction representative of a reduction in manifold pressure until the phase o2 balancing potential applied from the slider of potentiometer MP1 balances the new Value of phase p1 potential. Then the motor willV receive no further power impulses and will stop and relays RV and RVI will release. The synchro-transmitter ST land synchro-receiver SR will now have operated to reset the manifold pres- I sure indicator 100 to show a reduction of manifold pressure to about 22.5 inches of mercury representative of the reduction of manifold pressure incident to the operation of an engine at an idling speed of 500 R. P. M. on a closed throttle.

At the same time, with the ESTl relay 213 operated, the phase p1 potential derived at the slider of potentiometer RPMB is applied over the upper front contact of relay 213 and through summing resistor 253 to the signal input conductor 250 of the manifold pressure regulator motor unit but without effect since the shaft of such unit has previously been rotated to the position in which the L2 limit switch of such unit operated.

It will now be assumed that the pilot simulates the releasing of the brake and operates the throttle lever 1111 to open the engine throttle for warming up the engine and for taXiing. This movement of the throttle lever will not be sufficient to cause cam 113 to permit the associated contact set 113 to close and therefore the MPR relay 125 will remain unoperated. Cam 112, however, may permit the associated contact set i 15 to close, but this will be of no effect if the `Sylphon disable key 1132 at the instructors desk has not been operated, as it will be assumed.

The operation of throttle lever 111i will causev the movement of the sliders of the throttle potentiometers away from the No. 1 terminals of their windings. The movement of the slider of potentiometer T3 will be without eifect, however, since the WI relay 130 is assumed to be unoperated at this time. The movement of the slider of potentiometer T1. however, is eiective to decrease the phase :p2 potential applied over the circuit through the winding of the R. P. M. potentiometer RPMS extending from the slider of throttle potentiometer T1, back contact of the MPR relay 125, conductor 12'1, `and through resistor 226 to ground and in parallel through resistor 221 and the winding of potentiometer RPMd to ground. The winding of the throttle potentiometer T1 is energized in a circuit from the phase p2 bus bar through resistor 124, the potentiometer winding and resistor 125 to ground. With the engine now assumed to be running at an idling speed, a potential of phase o2 is now derived at the slider of potentiometer RPMS and applied through summing resist-or 228 to the signal input conductor 200 of the manifold pressure motor unit. This application of phase (p2 potential balances out a part of the phase p1 potential applied to conductor 20e from the slider of potentiometer RPMS and as a consequence the motor M is again controlled to turn shaft 2115 in a direction representative of a decrease in manifold pressure until the slider of potentiometer MPI readjusts the value of the phase e2 potential until it balances the phase pl potential. The manifold pressure indicator 1&0 will now indicate a manifold pressure of about 21 inches of mercury. The engine speed will now increase to about 1000 R. P. M.

At the same time the movement of the slider of throttle potentiometer T2 is effective to apply a phase p2 potential through summing resistor 252 to the signal input conductor 2511 of the manifold pressure regulator motor unit. To derive this potential. with the SHR relay 128 unoperated, a potential divider is established from the 40q 2 bus bar, through resistor 132 and over the upper back contact ci relay 129 to ground through resistor E33, from the junction point between which resistors 132 and 133 a circuit is established over the inner lower back contact of the SYF relay 128, through the winding of potentiometer T2, over the lower back contact of relay 129 and to amasar ground at the lower haeltv Contact of relay |28.; 'Ehe slider of; potentiometer T2 at this time es tahlishes a shunt of the upper portion oi the potentiometer Winding extending through the 130i) ohm resistor |34 and over the inner upper hack. Contact of relay |29. rlChe phase sp2' potenn tial. derived at the slider of potentiometerv T2 isv new applied over' the upper hackcontact of relay |33 and conductor l3| through summing' resistor 25.2 to the signaliinput conductor 25|) of the manif foldY pressure regulator motor unit. This phase p2ipotent'ial when" added' to the phase p2` potential applied through; summing resistor 25|' Will still he insufcienttobalance the phase p-l potential applied through resistor 2,53 With the result that the motor of. the: manifold pressure regun lator motor` unit will hold the, shaft of such. unit with the slider of: potentiometer MPR? at; the No.. 3 terminalv of the, potentiometer Winding.

It Willinow be assumed that the pilot operates the throttle lever till slowly; towards its open position to produce power for take-ofi When the throttle shaft Il l has rotated through 22 degrees theY cam |13 will permit the Contact set liti to operate to its closed position and, with the lrey lliat: the instructors desk in its normal position, a circuit is established from ground over contacts of such key, over contacts. of contact set l and through thev winding' of the MPR relayI |25 to battery'and ground'.

Relay |26` thereupon operates and disconnects the slider of the Tl throttle potentiometer from the previouslyA traced circuit over conductor [2l and through resistor 226 to ground from which phase (p2 potential was derived bythe potentiometerR-EMS and' applied through resistors 25| and 228. to the signal input conductors 258 and Zeil ofthe' manifold pressure regulator and manifold pressure motor units respectively, and establishesV acircuit from' the slider of manifold pressure regulator potentiometer' MPR'I', over conductor |35, over the` front. Contact of relay |26, conductor |21 and through resistor 22S to ground so that nowY the potential derived at: the slider of potentiometer RPMS and applied to signal input conductors 25@ and 200 is controlled by the manifold pressure regulator potentiometer MPR? rather than` by the throttle potentiometer TI'.

At' the. time throttle lever H'' has moved through 22 degrees of its SO-degree movement, the slider of the throttley potentiometer T2 Which'- isV capable of G-degree movement will have moved; through. 78.33r degrees and' the, phase @-2, potential derivedy at such slider will have. a value equal: toA the phase` :p21 potential. derived at` the slider of the. MPRl1 potentiometer which at this time is. at the No. 3 terminal of such potentiorrie-v ter Winding so that there will. be little or noy change in the. o2' potentialv applied through resisters 251i: and 223. to signal input conductors 255 and 2M. and' noohange in the indicated manifold pressure. To derive the phase 02 potential atY the slider of. potentiometer MPR?, which will match the potential derived at the slider or the throttle potentiometer Tl at 22 degrees of throttle opening, phase (p2: potential is applied from the 40p2 bus har, over conductor |36, through resistor 2d@ and through the potentiometer Windn ing to ground.

As thefthrottle lever it is slowly moved toward its. openl position for take-orf, a phase p2 potential of` increasing value is` derived at the slider of the. throttle potentiometer TZ which is applied overthe, loaclr` contact. of. the WI relay |39, over conductor lf3 i, and through the summing resistor 1 2 252 of themaniiold pressure regulator motor unit. The value oi this potential' at time is repre-k sentative oi" thei valueM of: the manifold pressure for any particular manoeuvre. For take-oii'the lever iiilwill be'moved until the manifold pres-` sure indicatorY shows a; manifold pressure of 54.5. inches of mercury. rlhe phase o2 potential thus derived is;v added. to the phase p2 potential derived at the slider of the rrianifoldl pressure regulator potentiometerMPRl, modified hy the R'. P; lvl. potentiometer'RPMd and applied through summing resistor 25|A to..l sign-al; input conductor 259' and, being W greater than thee phase (pi potential applied? tol conductor 25.@ through summing rey sister 253, whichV potential varies; with` the ine dioated air speed; =:vith. the altitude and with the engine speed, the motor of the manifold pressure regulatormotor unit will rotate theslider of potentiometerl MPRI'I- toward the; No. 1 termina-lof its winding to reduce the phase o2 potential derived at' such` slider; to maintain the summation oi the phase quil. potentials applied to conductor 253i balanced with` the phase qui po tential appliedI toconductor 2 5d.

The reduction. in phase p2 potential; derived at the slider of the manifold pressure regulator potentiometer MPR?? and modied, by the potentiometer RPMf in accordance: with the engine speed, isalso applied through summing resister 22-8ito signal input: conductor-2liii of the manifold pressure motor` unit and when addedto the phase p2 potential' derived at the' slider of the halancing potentiometer MP1 and applied to conductor 2G@ through. summing resistorI 233., will he reduced as=theI slider of potentiometer MPR-l is moved toward. the No. l terminali of its Winding with. the result that the phase pl` potential appliedC to conductor 2d@ from the sliderof potentiometer RPMEB. will become greater than the summa-tion of phase p2 potentials and; the motor M Willf turn shaft 235 in a direction representative oi an increase in mandold pressure; The rotation of shaft 2&5 through the operation of thefsynchro-transmitter ST and sylichro."receiver SR: will cause.- the reading oithemanifold pressure.v indicator iiito increase. As the manifold pressure increases, the enginev speed will increase and: in the; manner described in the applications hereinloeiore referred to, the sliders of the R'. P. M'. potentiometers RFD/ltr and RPMS will movetoward'the No. 3 terminals-.oi their windings` and, as air speed is developed.,` the slider of the indicated air speed potentiometer IAS? will also -l move towards the No. 3 terminal o its Winding.

The result of the,A movement of the sliders oi the potentiometers RPMi and I'ASilis tof increase the phase qll' potential applied to the signal in'- put conductorsI 22d and 255i' of the manifold pressure and manifold pressure regulator motor units asfy the manifold pressure increases.

The movement of the slider of, the RPM@ `potentiometeralso increases the phase qm2 potential derived at the slider of thelVlPRE potentiometer and applied from the slider or" potentiometer RP-Mtiv through resistor 255 to; the signal inputl conductor 25:3- as al measure.. of the loss in the intake manifoldsystem, which; loss increases as the: engine speed increases and causes a reductionV in the manifold pressure. potential derived at the slider of' potentiometer MPR? must thus compensate not only for the tender-Icyofthemanifold. pressure to decrease duel to the, manifold pressure intake loss represented by the; movementI of; the slid-er of poten- The phase p2 ifold pressure regulator motor unit will move thev slider of potentiometer MPRT towards the No. 3 terminal of its winding to increase the phase p2 potential derived thereat until it balances the phase p1 potential. This increase in phase p2 potential derived at the slider of potentiometer MPR'I being also applied through resistor 228 to signal input conductor Zell of the manifold pressure motor unit, the increased p1 potentialapplied through resistor 225 becomes balanced and the manifold pressure indicator |00 will therefore show no increase in reading as a result of the increase in engine speed and air speed.

lWhen the throttle lever has been moved through 75 degrees of its opening movement, the slider of the throttle potentiometer T2 Will have moved through 83.5 per cent of its movement. At that time the slider of the manifold pressure regulator potentiometer MPRT will have been returned toward the No. l terminal of its winding to reduce the phase q 2 potential applied through resistor 252 which with the phase p2 potential derived at the throttle potentiometer T2 will balance the phase p1 potential applied to control conductor 250. And the ground potential now applied from the slider of potentiometer MPRI will have caused the manifold pressure vmotor unit to set the manifold pressure indicator |00 to show the desired reading of 54.5 inches of mercury. When the critical altitude has been reached, the slider of potentiometer MPRT will have been returned to the No. l terminal of its winding representative of the full open carburetor throttle control and the further opening of the throttle lever H0 by the pilot is rendered of no avail by providing a short circuit of the last 16.5 per cent of the winding of throttle potentiometer T2 so that any further movement of the throttle through the last fteen degrees of its opening does not further increase the phase p2 potential derived by the potentiometer T2.

When take-off has been simulated, the pilot will close the throttle slowly until a manifold pressure oi about inches of mercury is indicated. The closing of the throttle will reduce the phase p2 potential derived at the slider of the throttle potentiometer T2 and as a consequence the balance between the phase p2 potentials and the phase qll potential applied to the signal input conductor 250 of the manifold pressure regulator motor unit will no longer exist and the phase p1 potential now predominating, the motor of such unit Will move the slider of potentiometer MPRl toward the No. 3 terminal of its winding therby increasing the phase p2 potential derived thereat and applied through resistor 25| to conductor 250 until the summation of the phase (p2 potentials again balances the phase pl potential.

The increase in phase p2 potential resulting from the movement of the slider of potentiometer MPRJ being also applied through resistor 228 to'the signal input conductor 200 of the manifold pressure motor unit, the motor M of such' unit is now controlled by the predominance of the phase p2 potential to move the slider of balancing potentiometer MPI towards the No. l terminal of its winding to reduce the phase p2 potential derived therefrom and applied through resistor 233 to conductor 2GB until the summation of the phase p2 potentials again balances the phase qll potential derived in accordance with :e new engine speed, as determined by the propeller governor, with the air speed and with the increasing altitude due to the simulated climb and applied through resistor 225 to conductor 263i). Under the control of the manifold pressure motor unit, the manifold pressure indicator |00 is reset to show a manifold pressure of cl0 inches of mercury.

As the altitude of the simulated flight increases the slider of the eltimeter potentiometer AIS will move slowly` towards the No. 3 terminal of its winding, thereby reducing the phase pl potential applied to the signal input conductors 200 and 250 of the manifold pressure and manifold pressure regulator motor units. Also upon the reduction of engine speed due to resetting of the propeller governor from the take-oir" to the climbing value of about 2600 R. P. M., the movement of the slider of the R. P. M. potentiometer RPM8 toward the No. l terminal of its winding, will also reduce the value of the phase p1 potential. In addition since a climbing manoeuvre is being simulated the indicated speed will be reduced whereby the movement of the slider of the indicated air speed potentiometer IAST toward the No. 1 terminal of its winding will also cause a reduction in the phase pl potential. With this reduction in phase pl potential, and with the phase 902 potential applied to conductor 251] under control of the throttle potentiometer T2, at a value determined by the pilot for a manifold pressure of 4i) inches of mercury. the motor of the manifold pressure regulator motor unit will now be operated in a direction to gradually move the slider of potentiometer MPR? towards the No. l

, terminal of its winding so that the potential of phase p2 derived therefrom will be gradually reduced to maintain a potential balance with the p1 potential applied to conductor 200 so that the manifold pressure motor will effectively maintain the manifold pressure reading at 40 inches of mercury as desired by the pilot and represented by the setting of the throttle potentiometer T2 by the throttle lever H0. Thus regardless of the change in altitude, the manifold pressure regulator motor unit will cause the manifold pressure indicator |00 to show a substantially steady manifold pressure reading. This condition will continue until the simulated ilight reaches a critical altitude at which time the slider of the potentiometer MPRI will have reached the No. 1 terminal of its winding whereafter no further balance of the phase p1 potential is eiective. If the altitude of the flight continues, as the phase el potential is further reduced by the altimeter potentiometer AIB, the phase qvl potential applied to conductor 200 of the manifold pressure motor unit will become less than the summation ofthe phase p2 potentials applied under the controler the balancing potentiometer MP]v and underthe control of the man1-e,

I5? fold pressure regulator potentiometer MPRT and' the motor'Mof the manifold pressure motor. unit will thereforelbe; operated in a direction to cause the indicator |90 to show a reduction in manifold pressure.

When this situation occurs the pilot, noting a reduction of manifold pressure or when he anticipates that the regulator will not maintain the. manifold pressure at the desired Value, will shiftA the supercharger blower to high blower speed byl the operation of the supercharger control |20 to its. high position thereby extinguishing the low speed lamp |06 at the instructors desk and closing a circuit from ground over its high Contact set and over the upper back contact of the SYF relay |28 through the winding of the SHR relay |29 to battery.V Relay |29 upon operating extends its operating ground overV its lower front contact and over conductor |31 through the winding of the SI-IRI relay 24| of the R. P. M. motor unit which in turn causes the operation of the SHR relay 235. Relay 24| also closes a circuit from ground over its inner contacts and conductor |38 through the high blower lamp |91 at the instructors desk to inform the instructor that the pilot has shifted the supercharger blower into high speed. The operation of the SHR relayl 2,35 establishes a new lower resistance circuit over which phase p1 potential is applied from the slider of the altimeter potentiometer Al 9- through the winding of the R. P. M. potentiometer RPMS. This circuit extends as previously traced from such slider to the back contact of the ALT relay 2| 9, thence over the upper iront contact of relay 235, through the Winding of potentiometer RPMB and over the lower front contact of relay 235 through resistor 238 toground. Also relay 235 establishes a y new shunt of the lower half of the winding of potentiometer RPMS over the inner upperv front contact of relay 235 and through resistor 242, which shunt is of slightly less resistance than the shunt which existed prior to the energization of relay 235. Also the 6800 ohm resistance shunt through resistor 243 of the winding of potentiometer RPM8 is removed at the middle upper back contact of relay 235. The total result of the change in the resistance network associated with potentiometer RPMS incident to the operation of'A relay 235- is to cause a. higher potentialvofv phase. qll, which increases at aA faster rate; as the engine speed' increases, to bederived at the. slider of potentiometer'V RPM8.

Theoperati'on of the SHR relay |29 establishes al newl Circuit overl which phasep2 potential is appli'ed from ground through' resistor |39, over the inner lower front contact of relay |29, through the` winding of potentiometer T2, over the, inner lower back'. contact, ofv relay |28 to the junction point between resistorsV |33 and'I |49 ofthe potential divider connected. from ground through resistor |33. and over the upper front contact of relay |29 through resistor |49 tov the 40 p2 bus bar. With relay |29- operated,- the. upper half of. the winding of potentiometerv T2 is shunted through the llic.- ohm resistor Hilf and over the inner.` upper front. contact of. relay |`29i and the formerr resistance shunt? from the: No. 3y terminal of the potentiometer Winding over the inner'v upper back contact of relay |29 and through resistor: |34 is opened. The result of the change in, the;v resistance-- networkv associated with the potentiometer T2- i's to cause a lower' potential of-phase yo-2,1 which increases atl a lower rate: as

thephase p2 potentials applied to signal input:

conductor 25|)- from the slider of' potentiometer T2 and from the slider of the manifold regulator potentiometer MPR? willy no longer balance the increased value of phase (p1 potential and the motor of the manifold pressure regulatormotorunit'will therefore in response to the predomi'- nant phase qui potential move the'slider of potentiometerMPRl toward the No. 3 terminal of its:

winding toA increase the phase o2 potential de'- rived thereat untila potential balance on conductor 259 is again secured.

The increase in= phase p2 potential now derived at the slider of potentiometer MPR? and applied tosignal input conductor 2te now tends to offsetV the increase' in phase pl potential due? toy the high blower manifold pressure schedule` to maintain the indicated manifold pressure' at;

the desired Value of 40 inches of mercury. If the climbing manoeuvre is continued, the further increase in altitude as represented by the movement of the slider of the altimeter potentiomfeter AIG continues to\ decrease the phase p1 potential applied to signal input conductor Zim-and, to maintain a potential balance on conductor 250, the manifold pressure regulator motor unit causes the movement of thev slider of potentiometer MPR? toward the No. l terminal of its winding thereby reducing the phase o2 potential derivedv at such slider and applied to signal input conductor 209` toA counterbalance reductionvin phase p1 potential applied to conductor 294|.' As` a resultv the manifold pressure motor unit main tains the indicated manifold pressure at 40 degrees ofmercury until the slider of potentiomA eter MPR? again reachesl its No. 1 terminal; rep' resentative of the critical altitude for thehigh. blower manifold pressure schedule.

From this point the manifold pressure regulator motor unit isineifective tomaintain the indi,- cated manifold pressure at l0 degrees oi mercury since as the altitude further increases and the phase (pl potential. decreases it is no longer possible ior the manifold pressure regulator potentiometer MPR?` to` further decrease the phase e2*` Consequently, as the phase cpl poten-- potential. tialappliedA to signalV input conductor 2te off the manifold pressure motor unit decreases, the motor. of such unit will be operated in a direction representative of ay decrease in manifold pressure which will be indicatedby the indicator |86.

The climbing manoeuvre continueV until` r`the ceiling altitude hasbeen reached, but the manifold pressure will continue to decrease withr a consequent reduction in engine` power and a slower rate of climb.

When `at anytime during the climbing manoeuvre, the pilot desires to level off the iiigllt for crusing, will manipulate the :flight controls to Cause the flight to level off and will gradually closethe throttle lever llt? untilY a manifold pressureA of` about' 24inches of mercury' is indicated and the engine speedl will be determined by the propeller governor at about 1800 revolutions per minute. It will be assumed that at the time the flight is thus leveled off, the supercharger blower is at high speed and that relays |29, |35 and 24| are all operated. With the closure of the throttle lever H0, the slider of throttle potentiometer T2 will be moved toward the No. 1 terminal of its winding thereby reducing the phase p2 potential derived thereat and applied to the signal input conductor 250 of the manifold pressure regulator motor unit. The summation of the phase p2 potentials now applied to conductor 250 will be less than the phase p1 potential applied to conductor 250 and to conductor 200 of the manifold pressure motor unit and consequently the motor unit will move the slider of the potentiometer MPRI toward the No. 3 terminal of its winding to increase the phase p2 potential derived thereat and applied to conductorsZUD and 250 until a potential balance on conductor 250 is again attained.

With this potential balance secured the phase (p2 potential derived at the slider of poentiometer MPRI and applied to signal input conductor 200 is effective to cause the motor M of the manifold pressure motor unit to turn the shaft 205 of that unit in a direction representative of a decrease in manifold pressure until the phase (p2 potential derived at the slider of balancing potentiometer MPI when summed with the phase o2 potential applied from the slider of potentiometer MPRI balances the phase p1 potential. When the manifold pressure as indicated by the indicator has been reduced to the desired value of 24 inches of mercury, the pilot will cease closing the throttle. Thereafter the manifold pressure regulator motor unit will function as previously described to maintain the indicated manifold pressure at 24 inches of mercury. If the simulated iight is at the critical altitude, the carburetor throttle is wide open and the slider of potentiometer MPR'I is at terminal I. To illustrate water injection, it should be employed at lower simulated altitude so that the water injection can cause an increase in manifold pressure as described in the following paragraphs.

Should the pilot require military power at this time he may secure such power by opening the throttle whereupon the manifold pressure will be increased as previously described in connection with the takeoff manoeuvre until when the manifold pressure of about 40 inches of mercury is secured the slider of the manifold pressure regulator potentiometer MPRT will have been returned to the No. l terminal of its winding representative of the full open position of the carburetor throttle. At such time the throttle lever ||D will have been moved through 75 degrees of its opening movement and further movement of the throttle lever will be of no avail, since the last 16.5 per cent or 70.33 degrees of the winding of the throttle potentiometer T2 is short-circuited and no further change in the phase e2 potential applied therefrom to the signal input conductor 25E! is possible at this time.

The pilot may, however, secure more power by using water injection. The use oi water injection in an engine has the beneficial result of cooling the engine to prevent it from overheating and l switch |22 thereby establishing the circuit of the WI relay |42. Relay |42 closes an obvious circuit for the "water injection on lamp |06 at the instructors desk and, if the anti-detonant key |0| at the instructors desk has been closed representative of the availability of water, a circuit will be closed from ground over the contacts of the MB relay |43, if relay |43 has been operated to simulate the availability of power to run the Water injection pressure motor, thence over the lower contacts of relay |42, over the contacts of key illl, over the upper contacts of the T relay |44, now operated from the contact set ||9 closed by cam ||8 with the throttle lever in a position beyond '75 degrees closure, thence over the inner upper back contact of the SYF relay |28 and through the winding of the WI relay |30 to battery and ground.

Relay |30 upon operating opens the circuit previously traced from the slider of throttle potentiometer T?. over which phase p2 potential was applied through the winding of potentiometer RPMS to provide a phase :p2 signal on the signal input conductor 250 of the manifold pressure regulator motor unit and establishes a circuit from the slider of throttle potentiometer T3 from which phase (p2 potential becomes applied over conductor |3| and through summing resistor 252 to conductor 250. To derive this potential, phase e2 potential derived at the junction point between the potential divider resistors |45 and |46, is applied through the winding of potentiometer T3 to ground. The potential available at the slider of potentiometer T3, at this time when the switchover is made to water injection and relay |30 operates, will be considerably lower than the potential derived at the slider of potentiometer T2 prior to the switchover and therefore there will be an abrupt decrease in phase p2 potential applied through resistor 252 to signal input conductor 250.

The summation of the phase p2 potentials now applied to conductor 250 will be less than the phase p1 potential and consequently the motor of the manifold pressure regulator motor unit will move the slider of potentiometer MPRT toward the No. 3 terminal of its winding until the phase e2 potential derived at its slider will provide a potential balance on conductor 25D. This increase of phase :p2 potential being applied to the signal input conductor 20D of the manifold pressure motor unit, will cause such unit to function in a manner representative of an increase of manifold pressure to 54.5 inches of mercury.

As the throttle lever is further moved toward its full open position the phase p2 potential derived at the slider of throttle potentiometer T3 will increase and as it increases the manifold pressure regulator motor unit will respond in the manner previously described to cause the potentiometer MPR? to decrease the phase p2 potential derived at its slider to maintain a balance between the phase el. and phase p2 potentials applied to conductor 25B whereby the decrease in potential applied to control conductor 200 of the manifold xpressure motor unit from the slider of potentiometer MPR? will cause the manifold pressure motor unit to control the manifold pressure indicator |00 to show an increasing manifold pressure above 54.5 inches of mercury. This will continue until the slider of potentiometer MPR'I reaches the No. l terminal of its winding at which time the indicator |00 will show no further increase in reading.

Simulation of failure of regulator servo systemv To simulate the disabling of the servo system of the manifold pressure regulator of an airplane, the instructor may operate key los athis desk thereby preventing the. operation of the MPR relay I when the pilot opens the throttle beyond the ZZ-degree angle at which time the manifold pressure regulator would ordinarily become operatve to automatically control the carburetor throttle. With relay 52d unoperated the continued opening of the throttle lever iiis effective through the throttlepotentiometer Ti to apply a decreasing value of phase (p2 potential to the signal input control conductors 2M and 258 of the manifold pressure and manifold pressure regulator r'motor units as it does during the first 22 degrees of the throttle travel and, as a consequence, the manifold pressure motor unit will respond to cause the movement of. the slider of balancing potentiometer MPR in a direction repe" resentative of an increase of manifold pressure. When, however, the throttle lever il@ has been moved to its full open position and the slider of potentiometer TI is at the No. 3 terminal of its winding, the manifold pressure motor unit will Simulation of failure of Sylphou bellows of the regulator The instructor may simulate the failure of the Sylphon bellows of the manifold pressure regulator by operating the key l B2. With this key operated, when the throttle lever H53 is operated by the pilot to a position representative of lany throttle opening greater than 9 degrees, cam H2 -will permit the closure of the associated contact set H5 thereby establishing a circuit from ground over the Contact of key lili, over the contacts of contact set H5 and through the winding of the SYF relay 28 `to battery. Relay it upon operating establishes an obvious circuit for the MPR relay IEE, opens the circuit of the WI relay H35 `at its inner upper back contact to prevent the operation of relay i559, and changes the resistance network associated` with the throttle potentiometer T2. rlhe operation of relay i253 establishes a new circuit for energizing the winding of potentiometer T2 which extends from the junction point between potential divider resistors ist? and itis, over the inner lower front Contact of relay itil, through the winding of potentiometer T2, over the lower back contact of the SHR relay 29, over the lower front contact of relay 28 and 'through resistor M9 to ground. As before, with theSHR relay |29 deenergized, representative of a low supercharger blower speed, thev upper portion. of the winding of the potentiometer is shunted over the inner upper back contact of relay i293, through resistor i3d and over the slider of the potentiometer. The changein the resistance network resulting from the operation of relay 12B is such that a sudden increase in the potential derived at the slider of potentiometer T2 takes place when relay t28 operates and this increase Ain phase c2 potential applied to the signal input conductor 255] of the manifold pressure regulator motor unit causes such motor unit to operate in a direction to move the slider Zd of potentiometer MPR'I back vtoward the No. 1 terminal of the winding to a. degree representative of the absolute drain oil pressure in the manifold pressure regulator of an airplane.

When the slider of potentiometer MPR? moves toward the No. l terminal, the |phase (p2 potential applied therefrom to the signal input conductor 26S of the manifold pressure motor unit is reduced and thereupon the phase cpl potential applied to conductor 2% becomes predominating. The motor M then rotates the shaft 255 in a direction representative of an increase in manifold pressure until the slider of the manifold pressure balancing potentiometer MP! has been advanced to a position in which the phase o2 lpotential applied therefrom balances the phase :p1 potential determined in accordance with the indicated air speed, altitude, and engine speed.

As the throttle is further opened the phase p2 potential derived at the slider of :potentiometer T2 will increase resulting in the operation of the manifold pressure regulator motor unit to move the slider of potentiometer MPR? farther back toward its No. l terminal thereby to maintain the balance between the phase (p2 potential and the phase pl potential applied to signal input conductor 259. The reduction-of the phase p2 potential derived at the slider of potentiometer MPR? being also effective at the signal input conductor itil of the manifold ypressure motor unit causes such unit to operate its balancing potential MP! in a direction to increase the balancing :potential of phase o2 derived thereat to maintain a potential balance on conductor 2t@ and to cause the manifold pressure indicator l5@ to show an increase in manifold pressure as the throttle opening increases.

When the throttle lever HB is moved back toward its closed position theslider of the throttle potentiometer T2 is moved back toward the No. 1 terminal of the potentiometer winding with the result that the manifold pressure regulator motor unit controls the manifold pressure motor unit in a manner representative of a gradual decrease in the manifold pressure indication representativev of the decrease in -manifold pressure which would result from the gradual closing of the carburetor throttle by the regulator in response to the closing of the pilots throttle lever. When the throttle lever l I@ is moved to a point in which the angle of opening is less than 9 degrees, cam l l2 permits Contact set l l5 to open to thereby release the SYF and MPR. relays l 29 and HES.

When relay 126 releases the phase o2 potential derived at the slider of the MPR? potentiometer is removed from the signal input conductor 260 of the manifold pressure motor unit and the phase p2 potential derived at the slider of the throttle potentiometer Tl is applied over the previously traced circuit to conductor 2M. This potential will be considerably less than the potential applied from the potentiometer MPR'I and as a consequence the manifold pressure motor unit will l function in a manner representative of the rather sudden decrease in manifold pressure which would result in an actual regulator due to the low boost look-out feature which enables a pilot to regain manual control of the carburetor throttle when low power is required for landing or taxiing operations.r

As the throttle lever is moved farther toward its full closed position the movement of the slider of potentiometer Tl is now effective to increase the phase o2 potential applied to conductor 26% thereby causing the manifoldfpressure to follow the throttle movement irrespective of the manifold pressure regulator motor unit.

The instructor may at any time cause a change in the manifold pressure indication for instruction purposes by the operation of the manifold pressure potentiometer MPP. The winding of this potentiometer is energized by phase p2 potential applied from the 40992 bus bar through resistor |513 and therefore the movement of the slider of this potentiometer is effective to derive a phase 02 potential and to apply it over conductor ll, over the upper front contact of the ESTZ relay 2l4 and through resistor 229 to the signal input conductor G of the manifold pressure motor unit which will cause such motor unit to operate in a manner representative of a reduction in the indicated manifold pressure.

In the preceding description it will he recalled that the phase rpl potential applied through resistors 225 and 253 to the signal input conductors 20o and 25H of the manifold pressure and manifold pressure regulator motor units was derived as a function of the indicated air speed at the indicated air speed potentiometer IAS'I, and that this potential increases to Vcause an increase in manifold pressure as the air speed increases. This simulates the ram effect which in an actual airplane causes an increase in manifold pressure as the air speed increases. It will be noted that due to the short-circuiting of the lower half of the winding of potentiometer IAS'l the phase el potential increases at a faster rate to cause a faster increase in manifold pressure as the air speed increases in simulation of the yfaster increase of manifold pressure in an actual airplane due to the ram effect as the air speed increases.

This phase el potential will also be slightly decreased to cause a slightly lower manifold pres sure indication if the pilot switches the operation of the engine to alternate carburetor air by causing the operation of the ALT relay S, since in an actual airplane a loss of manifold pressure is introduced when the pilot switches the carburet or air intake to alternate air thereby introducing some frictional losses which lower the intake air pressure at the carburetor.

What is claimed is:

l. In an aircraft trainer wherein the operation of an airplane engine under the control of a manifold pressure regulator is simulated, means operable representative of the speed of an airplane engine, means operable representative of the indicated air speed of a simulated night, means operable representative of the altitude of a simue lated night, a simulated throttle control lever, a source of current, means under the control of said throttle lever for deriving a potential of one phase from said source representative of a desired manifold pressure, means for deriving a potential of opposite phase from said source representative of the unregulated manifold pressure under the control of said engine speed simulating means, said indicated air speed simulating means and altitude simulating means, means for deriving a potential from said source of said first phase equal to the difference in said other poten-Y' tials, means for summariaing said latter two po tentials, and motor means responsive to said sumM mai-icing means for controlling other circuits and apparatus of the trainer to a degree representative of the desired manifold pressure.

2. In an aircraft trainer 'wherein the operation of an airplane engine under the control of a manifold pressure regulator is simulated, means operable representative of the speed of an airplane engine, means operable representative of the indicated air speed of a simulated flight, means operable representative of the altitude of a simulated flight, a simulated throttle control lever, a source of current, means under the control of said throttle lever for deriving a potential of one phase from said source representative of a desired manifold pressure, means for modifying said derived potential in accordance with a low or a high simulated supercharger blower schedule, means for deriving a potential of opposite phase from said source representative of the unregulated manifold pressure under the control of said engine speed simulating means, said indicated air speed simulating means and altitude simulating means, means for deriving a potential from said source of said first phase equal to the difference in said other potentials, means for surnmarizing said latter two potentials, and motor means responsive to said summarizing means for controlling other circuits and apparatus of the trainer to a degree representative of the desired manifold pressure.

3. In an aircraft trainer wherein the operation of an airplane engine under the control of a manifold pressure regulator is simulated, means operable representative of the speed of an airplane engine, means operable representative of the indicated air speed of a simulated flight, means operable representative of the altitude of a simulated flight, a simulated throttle control lever, a source of current, means under the control of said throttle lever for deriving a first potential of one phase from said source representative of a desired manifold pressure under which the simulated engine should be operated for low power output, means for deriving a second potential of opposite phase from said source representative of the unregulated manifold pressure under the control of said engine speed simulating means, said indicated air speed simulating means and altitude simulating means, means for summarizing said potentials, motor means responsive to said summarizing means to a degree representative of the unregulated manifold pressure at low engine power, means under control of said throttle lever after said lever has been operated beyond a predetermined open position for discontinuing the derivation of said first potential and for causing the derivation of a potential of the same phase from said source representative of a desired manifold pressure for high engine power, means for deriving a potential from said source of the same phase as said latter potential equal to the difference between said latter potential and said second potential, means for causing the summation of said latter potential and said second potential and the application of Said latter summation potential to said motor means for causing said motor means to control other circuits and apparatus of the trainer to a degree representative of the desired manifold pressure.

4. In an aircraft trainer wherein the operation of an airplane engine under the control of a manifold pressure regulator is simulated, means operalole representative of the speed of an airplane engine, means operable representative of the indicated air speed of a simulated night, means operable representative of the altitude of a sim ulated flight, a simulated throttle control lever, a source of current, a water injection simulation control key, means under the control of said throttle lever if said key has been operated for deriving a potential of one phase from said source representative of a manifold pressure desired under :a .water injection schedule,Y means Vfor lderiving a potential of -`opposite phase from said source representative of the unregulated manifold pressure under the control of said engine speed simulating means, said indicated air speed. simulating means and altitude simulating means, means for vderiving a potential from said source of said first phase equal to `the difference in said other potentials, means for summarizing said latteritwopotentials, and motor mea-ns responsive tosaid summarizing means for controlling other circuits and apparatus of the trainer to a degree representative of the manifold pressure desired under the Water injection schedule.

5; In an'aircraft trainer wherein the operation of "an airplane engine under the control of a manifold pressure regulator is simulated, means operable representative Yof the speed of an airplane engine, means operable representative of the indicated air speed of a simulated flight, means operable representative of the altitude of a simulated flight, a simulated throttle control lever, an instructors desk, a key at said desk operable to represent the availability of the water supply for water injection, a switch operable to represent the availability of power to operate a water injection 'pressure pump, a simulated water injection control key, a source of current, means under the control of said throttle lever if said keys-and saidv switch have been operated for deriving a potential of one phase from said source representative of a manifold pressure ydesired under a water injection schedule, means for deriving a potential of opposite phase from said source representative `of the unregulated manifold pressure'under the control of said engine speed simulating means, saidA indicated air speed simulating means and altitude simulating means, means for deriving a potential from said source of said first phase equal to the difference in said other potentials, means for summarizing said latter two potentials, vand motor means responsive to said summarizing means for controlling other circuit-s and apparatus of the trainer to a degree representative lof the manifold pressure desired under the water injection schedule.

6. In an aircraft trainer wherein the operation of an airplane engine under the control of a manifold pressure regulator is simulated, means operable representative of the speed of an airplane engine, means operable representative of the indicated air speed of l a simulated flight, means operable representative of the altitude of a simulated iight, a simulated throttle control lever, a source of current, a water injection simulation key, means under thecontrol of said 'throttle lever if said key has been operated and said throttle has been opened through a predetermined angle for deriving a potential of one phase from said source representative of a manifold pressure desired under a water injection schedule, means for deriving a potential of opposite phase from said source representative of the unregulated manifold pressure under the control of said engine speed simulating means, said indicated air speed simulating means and altitude simulating means, means for deriving a potential from said source to said rst phase equal to the difference in said other potentials, means for summarizing said latter two potentials, and motor means responsive to said summarizing means for controlling other circuits and apparatus ofy the trainer to a degree representative of the manifold pressure desired under the water injection schedule.

7. In an aircraft tranerwherein the Aoperation of-an airplaneengine under f the control'of .a manifold pressure regulator is -fsi-mulated, means operable representative of the speed of an fairplane engine, means operable representative of the indicated air speed Yof a simulated flight, means operable representa-tive of the altitudeof a simulated -ight, aisimulated throttlel control lever, a source of lcurrent, mea-ns under the lcontrol of said throttlelever for Aderiving a .potential of one phase from-said source representative of a desired manifold pressure, means for .deriving a potential of opposite phase from said source representative of theunregulated manifold rpressure underthe lcontrol of said engine speed simulating means, said indicated air 4speed simulating means and altitude simulating means, means for deriving a potential from said source of said rst phase equal tov the-dilferencein said `other potentials, means for summarizing said latter two potentials, motor means responsive-to said summarizing means for controlling other vcircuits and apparatus of the trainer to a degree .representative of the desired manifold pressure, means for deriving a potential of said rst phase from said source under the control of said throttle lever, and a key for simulating the failureof the servomechanism of the manifold pressure regulator effective to discontinue the derivation of said first potential and to render the vsummation of said latter and said secondpotentials effective to control said motor means to va degree representative of the unregulated manifold pressure determined by the setting `of said throttle lever.

8. In an aircraft trainer wherein the operation of an airplane engine under the control of a manifold pressure regulator is simulated,` means operable representative of the speed of an airplane engine, means operable representativeof the indicated air speed ofA a simulated flight, means operable representative `of the'altitude of a simulated flight, a simulated throttle control lever, a source of current, means under'the control of said throttle lever for deriving a first potential of one phase from said source'representative of a desired manifold pressure, means for deriving a potential of opposite phase from said source representative of the unregulated manifold pressure under the control-of said `enginespeed'simulating means, said indicated air speed simulating means and altitude simulating means, means for summarizing said derived potentials, a first motor driven means responsive to said summarizinT means for deriving a potential from said source of said first phase equal to the difference in said other potentials, means for summarizing said latter two potentials, a second motor means responsive to said latter'summarizing'means for controlling other circuits and apparatus of the trainer to a degree representative of the desired manifold pressure, a key for simulating the failure of the Sylphonbellows of a manifold pressure regulator, and means controlled by said key for altering said first potential deriving means to increase said first potential to a `degree representative of the pressure leakage of the disabled bellows whereby saidlatter motor driven means is controlledon a different schedule for controlling other circuits and apparatus in the trainer to a degree representative of the desired manifold pressure.

9. In an aircraft trainerwherein theoperation of an airplane engine'under the control of a manifold pressure regulator .is simulated, means operable representative .ot the speed. kof `an air;- plane engine,V means `operable -representative of the indicated air speed of a simulated flight, means operable representative of the altitude of a simulated flight, a simulated throttle control lever, a source of current, means under the con'- trol of said throttle lever for deriving a rst potential of one phase from said source representative of a desired manifold pressure, means for deriving a potential of opposite phase from said source representative of the unregulated manifold pressure under the control of said engine speed simulatingT means, said indicated air speed simulating means and altitude simulating means, means for summarizing said derived potentials, a first motor driven means responsive to said summarizing means for deriving a potential from said source of said first phase equal to the difference in said other potentials, means for summarizing two potentials, a second motor means responsive to said latter summarizing means for controlling other circuits and apparatus of the trainer to a degree representative of the desired manifold pressure for high engine power, a key for simulating the failure of the Sylphon bellows of a manifold pressure regulator, means controlled by said key for altering said first potential deriving means to increase said first potential to a degree representative of the pressure leakage of the disabled bellows whereby said responsive latter motor driven means is controlled on a different schedule for controlling other circuits and apparatus of the trainer to a degree representative of the desired manifold pressure, means for deriving a potential of said first phase from said source under the control of said throttle lever, and means controlled by said throttle lever when it is moved to a predetermined position in its closing movement to disable said key controlled means, discontinue the derivation of said first potential and to render the summation of said latter and second potentials effective to control said second motor driven means for controlling other circuits and apparatus of the trainer to a degree representative of the unregulated manifold pressure determined by the setting of said throttle lever for low engine power.

10. In an aircraft trainer wherein the operation of an airplane engine under the control of a manifold pressure regulator is simulated, means operable representative of the speed of an airplane engine, means operable representative of the indicated air speed of a simulated flight, means operable representative of the altitude of a simulated fiight, a simulated throttle control lever, a source of current, a control conductor, means under the control of said throttle lever for deriving a potential of one phase from said source and for applying it to said conductor, means for deriving a potential of opposite phase from said source representative of the unregulated manifold pressure under the control of said engine speed simulating means, said indicated air speed simulating means and altitude simulating means, and for applying it to said conductor, a potentiometer for deriving a potential from said source of said i'lrst phase equal to the difference in said other potentials and for applying it to said conductor, a motor responsive to an unbalanced potential condition on said conductor for adjusting said potentiometer until the sum of the potentials applied to said conductor becomes zero, means for summarizing said latter two potentials, and motor means responsive to said summarizing means for controlling other circuits and apparatus of the trainer to a degree representative of the desired manifold pressure.

11. In an aircraft trainer wherein the operation of an airplane engine under the control of a manifold pressure regulator is simulated, means operable representative of the speed of an airplane engine, means operable representative of the indicated air speed of a simulated flight, means operable representative of the altitude of a simulated flight, a simulated throttle control lever, a source of current, a control conductor, means under the control of said throttle lever for deriving a potential of one phase from said source and for applying it to said conductor, means for deriving a potential of opposite phase from said source representative of the unregulated manifold pressure under the control of said engine speed simulating means, said indicated air speed simulating means and altitude simulating means, and for applying it to said conductor, a potentiometer for deriving a potential from said source of said first phase equal to the difference in said other potentials and for applying it to said conductor, a motor responsive to an unbalanced potential condition on said conductor for adjusting said potentiometer until the sum of the potentials applied to said conductor be- 'comes zero, a second control conductor to which said latter two potentials are applied, a balancing potentiometer for deriving a potential of said first phase from said source and for applying it to said latter conductor, a second motor operable in response to the unbalanced potential condition on said latter conductor for adjusting said balancing potentiometer until the sum of the potentials applied to said conductor becomes zero, and a simulated manifold pressure indicator controlled by said latter motor to indicate the desired regulated manifold pressure.

12. In an aircraft trainer wherein the operation of an airplane engine is simulated, means operable representative of the speed of an airplane engine, means operable representative of the indicated air speed of a simulated flight, means operable representative of the altitude of a simulated flight, a source of current, means for deriving a potential from said source under the control of said indicated air speed and said altitude simulating means which varies in accordance with the indicated air speed and altitude of the simulated flight in simulation of the ram effect on the manifold pressure produced in the night of an airplane, means controlled by said engine speed simulating means for modifying said latter potential in accordance with the simulated engine speed, and motor means responsive to said modified potential for controlling other circuits and apparatus of the trainer to a degree representative of the manifold pressure.

13. In an aircraft trainer wherein the operation of an airplane engine is simulated, means operable representative of the speed of an airplane engine, means operable representative of the indicated air speed of a simulated flight, means operable representative of the altitude of a simulated flight, a simulated throttle control lever, a control conductor, a source of current, means responsive to said throttle lever for deriving a nrst potential from said source and for applying it to said conductor which varies with the throttle opening, means for deriving a second potential of opposite phase from said source and for applying it to said conductor under the control of said indicated air speed and said altitude simulating means which varies in accordance with the indicated air speed and altitude of the simulated night in simulation of the ram effect on the manpotential of thesame phase as said rst potential from-'said source and for applyingit to said con- I; ductor, a motor responsive to an unbalancedipotenti'al condition on said conductor to adjust said potentiometer until thesum of the potentials appliedftosaid conductor becomeszero, and a, simulated.- manifold pressureindicator operable by saidmotor.

14. In an aircrafttrainer wherein the operation off-an airplane engine is simulated, means oper- `ablerepresentative of thespeed of an. airplane engine, means operable representative ofv the indicated air speedwof a simulated flight, means operable-representativeof the altitude of a simulated flight, asource of cur-rent, means controlled by said indicated.y air speed simulating means for deriving-Aapotential from said. source Which increaseslat an increasing. rate as tliev air speed of alsimulated-fflight increases, means controlled by said altitude simulating means for modifying said` potential in'accordance lwith the altitude of thesimulatediiight whereby said modied poten- 28 tial' Varies in-l simulation. offl the ramect on the manifold pressure` producedy nthe. flight of an airplane,` means controlled byesaid engineV` speed simulating. meansr forflirt-hen modifying saidA potentialv in accordance; with thesimulated engine speed,andl motor means responsive tosaid latter potential for controlling` other circuits` and apparatus of thetrain'erto a degree. representative of the manifoldpressure.

`JOSEPH J; LUKACS.

REFEREMISES. CITED;

The followingVv references are of record in'the le ofthis patent:

UNITED. STATES PATENTS Number Name Date 2,099,857 Linkl Nov. 23, 1937 2,332,523; Norden- Oct. 26, 1943 2,346,838' "Haight Apr. 18, 1944 2,366,603 Dehmel Jan; 2, 1945 2,372,741 Roberts- Apr; 3. 1945 2,395,477 Gumley Feb. 26, 1946 2,406,936' Holden; Sept. 3 1946 2,408,081v Lovell Sept. 24, 1946 2,428,767l Albert 'Oct; 14, 1947 2,439,168 Kail Apr, 6, 1948 

